Question

The table shows the battery life of four different mobile phones:

Mobile Phone Battery Life Phone
Battery Life (hours)
A 20
B 25
C 10
D 18
If 8.45% of the battery life of each mobile phone is used in a day by a typical user, which mobile phone would use a total of 1.69 hours of battery life in a day?
Phone A
Phone B
Phone C
Phone D

Answer 1

Using quick mental math, we can do 8% of 10 to get 0.8, which is close to the value of 0.0845*10. Also fairly quick is moving the decimal point over 1 spot to the right and we go from 0.0845 to 0.845 and that rounds to 0.8 when rounding to one decimal place. Recall that 8.45% = (8.45/100) = 0.0845

If you want to compute out the four results with a calculator, then it would look like this:

0.0845*20 = 1.69

0.0845*25 = 2.1125

0.0845*10 = 0.845

0.0845*18 = 1.521

and this shows that no other result (but choice C) is close to 0.8

So that's why the answer is choice C

Explanation: